1. Field of the Invention
The present invention relates to slide exercise devices, and in particular to the configuration and positioning of bumpers of slide board type exercise devices.
2. Description of the Related Art
Slide board exercise devices are typified by U.S. Pat. No. 4,779,862 and 5,114,387 to Keppler. These devices were developed primarily as exercisers for speed skaters and similar athletes. The basic apparatus has a rectangular base covered with a plastic sheet. The plastic sheet has a smooth glide surface which is bounded at two sides by a bumper at each end of the sheet. The bumpers are attached to opposite ends of the base along the two shorter sides of the rectangle.
A person wearing the appropriate footwear (socks or shoe covers) slides along the plastic sheet until one foot contacts a bumper. By pushing with the leg contacting the bumper, the person can slide again along the plastic sheet in the other direction until the other foot contacts the second bumper. By alternately pushing off of one bumper towards the other bumper, the person exercises the muscles of the legs and other muscles.
Early prior art slide boards comprised a base and two bumpers. The bumpers were rigid and removable members clamped to the ends of the base. The bumpers were mounted parallel to each other and had vertical surfaces which received the impact of the sliding feet. A problem with the above-mentioned configuration was that the vertical bumpers caused considerable and adverse impact pressures and stresses to be applied to the foot, ankle and knee. During impact, the fifth metatarsal of the foot contacts the rigid vertical wall of the bumper. This initial impact causes bruising of the side of the foot, which eventually results in user discomfort and diminishes the utility of the slide board. If contact with the bumper continues, unwanted lateral pressure increases on the subtalar joint and on the knee, stressing the lateral collateral ligament.
These disadvantages were somewhat addressed in the second patent to Keppler, No. U.S. Pat. No. 5,114,387. This patent discloses a slide board having an inclined plane attached to and adjacent to the bumper. The ramp section of the bumper is made of wood and is inclined at an angle relative to the horizontal such that the ball of the foot, rather than the metatarsal bones, contact the bumper. Thus, side impact pressure and lateral stresses are reduced. On deceleration, the ball of the foot will contact the bumper and the ankle will attempt to evert to the angle of the inclined plane bumper.
The flexibility of a typical ankle will permit a maximum eversion of approximately 20 degrees. Eversion of more than 20 degrees generally causes pain. Medical experts have suggested that the maximum range for the ankle to evert, which is the maximum strain load before injury, is between about 15 and 20 degrees. Prior art inclined bumpers are inclined at an angle of 25 to 40 degrees. Angles of this magnitude were required to create sufficient lateral stopping force. However, impact with such a bumper causes the ankle to evert more than 20 degrees and results in pain. To compensate for the pain, the user changes (decreases) the normal hip height to decrease the angle to which the ankle must evert after impact with the steep ramp. This altered position of the leg and body decreases the effectiveness of the exercise and may lead to other injuries. Thus, the prior art slide board devices have addressed the problems of bruising of the foot and lateral stresses on the ankle and knee, but the solution is unsatisfactory because it causes further stress on the ankle and causes poor body position during exercise.
Another deficiency of the early prior art slide boards is that the bumpers are parallel to each other at the ends of the plastic sheet. However, the tendency of the foot is to naturally turn outward slightly as the user pushes off. Thus, ideally, the bumpers should be toed-out slightly to allow the user to push off comfortably and remain aligned upon the slide board. Prior art slide board exercisers such as U.S. Pat. No. 4,779,862 were designed primarily for speed skating, and provide for a fixed toe-out of 10.degree.. Thus, some prior art slide boards have addressed the need for a toe-out angle to provide for a natural push-off position for the foot, but fail to provide an adjustable toe-out angle or optimum toe-out angles for the motions of specific exercise. A modern slide board exerciser should permit a wide variety of exercises and should permit adjustment to the appropriate toe-out angle.
Yet another deficiency of the prior art is that the slide boards limit the user's motion to lateral side-to-side motions in one direction. The rectangular base is bounded only at two opposing sides, thus giving the user no freedom to exercise by pushing in forward, rearward or diagonal positions.
Yet another deficiency of the prior art is that traditional bumpers are made of wood and comprise a vertical wooden bar with a wooden wedge attached to the vertical surface of the bar. This design requires at least two attachments, one for attaching the bar to the plate, and another for attaching the wedge to the bar. Additional components such as pads between the wedge and the bar function as shock absorbers. Thus, the prior art slide boards have many parts and connections which make the device expensive to manufacture and difficult to assemble and maintain.